(A) 1 Ω
Maximum resistance is obtained by connecting all resistors in series: $R_s = 5 \times \frac{1}{5} = 1\ \Omega$.
Series combination always gives the maximum equivalent resistance (sum of all individual resistances), while parallel gives the minimum. Here, $5 \times \frac{1}{5}\ \Omega = 1\ \Omega$. Source: Chapter 11, Section 11.6.1 — Resistors in Series.